Spark plug



N. 5 HARPER May 21, 1957 SPARK PLUG Filed larch 3, 1954 R n R OR B MA H R; 0

m 4 4 Mr. H m w n B A l 7 66 L 4 I FIG. 3.

FIG.- I.

SPARK PLUG Niles E. Harper, Wendel, Pa. Application March 3, 1954, Serial No. 413,744

Claims. (Cl. 313-115) This invention relates to spark plugs, particularly adapted for use in internal combustion engines.

While it has been proposed heretofore to apply a heat ing element adjacent to the porcelain core of a spark plug in order to eifect improvements in the operation of such spark plugs, such proposals have only resulted in limited benefits. In particular, the heating of the porcelain by the closely disposed heating element produces but little improvement in the operation of an internal combustion engine. Much of the heat produced by the element is absorbed by the porcelain, and while this may improve the electrical insulation resistance of the porcelain, it has little efiect on the ignition of the combustible gases by the spark plug.

At the present time, the carburetors of internal combustion engines are so constructed that under starting conditions an abnormally large quantity of fuel is fed into the combustion chamber. This is designated as choking, and often results in flooding of the combustion chamber. Ignition is difficult, if not impossible, when the combustion chamber is flooded with fuel. At abnormally low temperatures, water may be present in the combustion chamber. poorer at lower temperatures and combustion is thereby less liable to occur. The presence of excess fuel and water also render starting an increasingly diflicult problem as the temperature drops. Both automatic chokes and hand choking fail to take into account these various circumstances adverse to proper engine starting, so that their action makes starting more of a problem at low temperatures such as are met in winter.

The object of my invention is to provide a spark plug with a heating means disposed around the spark gap, but spaced away from the spark plug proper and into the combustible gas, whereby a substantial spherical zone of the combustible gas mixture adjacent to the igniting spark gap is heated and thereby rendered more perfectly and rapidly combustible than would otherwise be possible, particularly under adverse conditions.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

For a better understanding of the nature and objects of the invention, reference should be had to the following detailed description and drawings, in which all the figures have been greatly enlarged:

Figure 1 is a view in elevation partly in cross section of a spark plug in accordance with my invention,

Fig. 2 is a bottom plan view,

Fig. 3 is a top plan view, and

Fig. 4 is a view in elevation partly in section of a modified spark plug construction.

In accordance with my invention, a spark plug is provided with a heating element surrounding the spark gap which is adapted to be energized with low-voltage highamperage current from a suitable battery or other source of electrical energy, the heating element being located beyond the usual body of the spark plug and into the combustion chamber so as to heat a substantial volume ted States Patent 0 The vaporization of the fuel is progressively l atented May 21, 1957 of combustible gas adjacent to and surrounding the ignition spark gap of the spark plug. 'By this means substantially all of the heat developed in the heating element is applied to the combustible gas immediately about the spark gap so that only a relatively negligible proportion of the heat is absorbed by any portion of the spark plug proper. Any unvaporized gasoline is converted to gaseous vapor.

Referring to Fig. 1 of the drawing, there is illustrated one modification of a spark plug 10 constructed in accordance with my invention. The spark plug 10 comprises an insulating porcelain body 12 carrying along its axis an electrode 14 which is connected to the contact 16 receiving electrical current from a suitable wire from a distributor or other source of electrical voltage current, as is well known. The porcelain body 12 comprises an upper portion 18, an enlarged central portion 20, and a lower tapered portion 21. The enlarged central portion 20 is provided with an upper shoulder 22 and a lower shoulder 24 against which are applied gaskets 26 and 28, whereby the porcelain is retained in gas tight relationship within a hexagonal metal body 30. A flange 32 spun over the gasket 26 serves to retain the porcelain rigidly within the hexagonal metal shell 30.

A longitudinal passageway 36 is formed through one side of the enlarged portion 20. A metallic conductor 38 provided with suitable sealing insulation 40, such as a ceramic refractory, projects through the passageway 36. The upper end of the conductor 38 is aifixed to a peripherally slotted contact 42 encircling the portion 18 with an insulating ring 44 of mica, asbestos, or other material being disposed to insulate it from the flange 32. A lead 46 connected by a manually operated switch (not shown) to a storage battery or other source of low voltage, high-amperage electrical enregy is provided with a spring clip 48 adapted to fit resiliently within the peripheral slot of the contact 42 whereby good electrical contact is maintained. Extending below the metal shell 30 is a threaded cylindrical portion 50 enabling the spark plug to be threadedly inserted into the cylinder head 62 or the like of an internal combustion engine. At the lower end of the cylindrical portion 50 is a bent electrode tip 52 adapted to cooperate with the tip 54 at the bottom of the electrode 14, to form a spark gap therebetween. The conductor 38 terminates in a projection 56 bearing a heating ring 58 of a suitable resistance metal, such, for example, as platinum or the well known 2080% chromium-nickel alloy. The side of heating ring 58 opposite to the projection 56 is aflixed to the electrode tip 52. It is evident that a substantial space 60 separates the heating ring 58 from the cylindrical portion 50. The ring 58 may be a /2 inch diameter ring of inch wide strip of a thickness of 0.020 inch.

In operation of an internal combustion engine fitted with the spark plug of this invention, when low voltage, high amperage electrical current passes through the lead 46 to contact 42, thence to conductor 38 and finally to the heating ring 58, and then to ground via tip 52 and portion 50, the ring 58 will become hot and within a few seconds the adjacent body of combustible gas will become heated thereby to a substantial temperature. The isothermal lines of circumambient gas heated by the ring will be of the shape generally indicated by the dotted lines 64, with the maximum temperatures being substantially adjacent the ignition spark gap between 52 and 54. Under these conditions, if high-voltage current is passed through the spark gap combustion of a combustible gas mixture within the volume indicated by 62 takes place promptly and efficiently.

I have discovered that a very brief flow of current through the heating ring 58, for example, for a few seconds, is adequate to cause an internal combustion engine to start promptly and to operate without any difficulty even in exceptionally cold and difiicult conditions. As is well known, small internal combustion engines of the type used for lawn mowers are quite difficult to start in cold weather, and especially after they havebeen out of use for considerable periods of time. Spark plugs constructed in accordance with my invention, as shown in Fig. 1, have been applied to such small motors, and I have had no difliculty in causing them to start on the first spin of the flywheel and to keep operating thereafter without fail atall times. Usually, I have passed heating current through the lead 46 to the heating ring 53 for a few seconds, turned over these motors once and have had them start and keep running promptly. After the motor has operated for seconds or so, I have opened the switch to the lead 46 to interrupt flow of electrical current to the heating ring 53, and the motors have continued to operate successfully. In other cases, I have left the current flowing to the heating ring 53 throughout the entire period the engine was kept in operation.

My invention is particularly well adapted for use in automobile engines, motor boat engines, and aircraft and fire engines which are subjected to dampness and extreme ly low temperatures. The heating ring 58 may he energized for a few seconds or so and then the engine turned over, whereupon it will fire properly and run successfully. I have made tests of the spark plug provided with the heating element in internal combustion engines at low temperatures and found them to enable easy and prompt starting where otherwise the motor must be turned over many times. Without the spark plug, the motor will often fire weakly once and then stop and require several starting operations before successful and continuous operation occurs.

Referring to Fig. 4 of the drawing, there is illustrated a modified spark plug 100 having a porcelain body 102 within which is disposed a high voltage electrode 104 through which ignition current passes and a low voltage conductor 106 through which low voltage heating current passes, both of the conductors being molded or atfixed within the porcelain simultaneously and fired as is well known. A peripherally slotted contact 112 is $01- dered or welded or otherwise aflixed to the upper end of the conductor 106. The electrode spark tips 114 and 116 function to ignite the combustible mixture. The lower end 108 of the conductor 106 is welded or affixed to a downwardly projecting heating ring 110 spaced from the spark plug body proper. Also, a single loop may extend downwardly from 1.08 to 116. Otherwise the function and operation of the plug modification of Fig. 4 p

the body 12 and 102, for example, mica and glass may be employed. The construction and assembly of the spark plug may enable it to be taken apart or otherwise suit requirements. While the heating ring 58 is shown as being circular, it will be appreciated that it can be elliptical, hexagonal or of other shape.

I claim as my invention:

1. A spark plug compn'sing a refractory insulating body, with a first electrode passing through the body, the upper end of the electrode being provided with a contact to receive a lead wire, a metal shell disposed about refractory insulating body, the metal shell terminating in an open ended, threaded cylindrical portion surrounding both the lower end of the porcelain body and the lower end of the first electrode, a second electrode attached to the cylindrical portion and ending adjacent to the lower end of the first electrode to form therebetween a spark gap, a conductor passing through the refractory body, the conductor having an upper end affixed to a contact adjacent the upper end of the metal shell, the lower end of the conductor affixed to a heating element to conduct electrical current thereto, the heating element being composed of an electrically resistant metal, means at the portion of the element opposite to the part affixed to the conduct-or connecting it to the lower end of the cylindrical portion, the heating element being disposed below and spaced from the cylindrical portion whereby when electrical current is passed from the conductor to the heating element the element is highly heated and thereby heats adjacent gases, the heating element having approximately the resistance between diametrically opposed points of a ring of /2 inch diameter and of a cross-section of inch by 0.020 and of 20%-80% chromium-nickel alloy, whereby the heating element may be operated directly from a storage battery simultaneously while sparle ing current is supplied to the first electrode without the heating element causing misfiring.

2. The spark plug of claim 1, wherein the means connecting the heating element to the cylindrical portion includes the second electrode.

3. The spark plug of claim 1, wherein the contact at the upper end of the conductor is a peripherally grooved ring encircling the refractory insulating body.

4. The spark plug of claim 1., wherein the heating element is a circular ring.

5. The spark plug of claim 1, wherein the heating element is a downwardly extending loop.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,185 Goodheim Sept. 5, 1933 2,046,650 Nowosielski July 7, 1936 FOREIGN PATENTS 434,782 Great Britain June 4, 1934 

